Amines as gel-shrinkage reducing



Dispersion A:

Reiuued May 12, 1953 AMIN ES AS GEL- SHRINKAGE REDUCING AGENTS INSYNTHETIC-RUBBE-R SPONGE Leonard A. Wohler, Bath Township, SummitCounty, and Ernst Schmidt, Akron, Ohio, assignors to The Firestone Tire& Rubber Company, Akron,

Ohio, a corporation of Ohio No'Drawing. Original No. 2,537,645, datedJanuary 9, 1951, Serial No. 7556;55'6, June 23; 1947.

Application for reissue January 8, 1952, Serial 14 Claims. (Cl; gem-2.5)

- Hatter enclosed in heavy brackets I: appearlin" the original patentbut-forms no part 01". reissue specification; matter printed in italicsindieates'th'e additions made by reissue.

This invention relates to the production of foamed latex spongeproducts. such as seat mattresses, cushions, etc. The latex employed ispreferably a latex of GWS which may contain latex ofnatural rubber.Instead of GRL-S latex there may be'used' the latex of other rubber-likecopolymer of a conjugated diene--for example, butadiene, piperylene,cyclopentadiene, dimethylbutadiene, isopren'e, 2-cyanobutadiene,Z-methyI-L3-pentadiene, etc.-and avinyl aromatic compound-4hr example,styrene, alphamethylstyrene, nuclear-substituted styrene,monochlorcstyrene, dichlorostyrene, vinylbiphenyl, vinylcarbazole,vinylnaphthalene, 2-vinyl-5-ethylpyridine, 2-ethy1-5-vinylpyridine, etc.The latex is obtained by emulsion copolymerization of the monomersmentioned.

One very troublesome defect encountered in the making of foamed latexsponge is that known as gel shrinkage. This shrinkage occurs during thegelling or curing period, and it is greater in sponges made from latexof a copolymer of a con- Jugated diene and a vinyl aromatic compoundthan in that from other latices. The sponge made from such latex mayshrink as much as 50 per cent in volume. Defective products result fromsuch shrinkage, and although various attempts have been made toeliminate it or minivmize the damage which results from it, no entirelysatisfactory solution has heretofore been developed.

In has now been found that gel shrinkage in roamed sponges made fromsuch latices can be greatly reduced if there is incorporated in thefoamed latex from which the sponge is formed an amine from the classconsisting of cyclohexyl, benzyl, ,n-propyl, n-butyl, and n-amyl amines.The amine may be used in the form of -a fatty acid soap of the amineobtained from any soap-forming fatty acid, such as, for example,

oleic, stearic, palmitic or ricinoleic acid, etc.

The preparation of the sponge may, in general, follow the procedure ofthe example which follows. The compounding ingredients are preferablydispersed in aqueous dispersions and then mixed. The following, in whichthe weights are given as dry weights and the amount of water in eachdispersion is given in the parenthetical explanations, is illustrative:

, Parts by weight Cyclohexyl amine 3 Potassium castor oil soap (35%aqueous dispersion) 2. Dispersion B:

Sulfur (50% aqueous dispersion) 2.

Piperidine pentamethylene dithiocarbamate (40% aqueous dispersion)..

Sym. di-p-naphthyl-paraphenylenediamine (40% aqueous dispersion)Dispersion C:

GR-S latex (aqueous dispersion containing 55% copolymer of 70% butadimeand 30% styrene) 100 Dispersion D:

Zinc-oxide (50% aqueous disperslon) 5 Dispersion E:

Sodium silicofluoride (50% aqueous dispersion) 2.5

' alkyl chain and a mixture of monosodium salt of polymerized arylalkylsulfonic acids and inorganic suspending agent, known respectively asDaxad No. 11 and Daxad No. 27, manufactured by Dewey and Almy ChemicalCompany, of Cambridge,-Massachusetts, are mentioned as dispersing agentswhich may be employed.

Dispersion A is then added to dispersion B with stirring. The resultantis added to GR-S latex. Dispersion D is then added. The resultant is setaside to mature. It matures relatively rapidly. the maturing beingcomplete in 24 hours at 25 C. The dispersion is then whipped to a foam.The mixer, known as Hobart M430, may be used for this purpose.Dispersion E is then stirred in. Two and a half parts of the fluoride-4.e., 5 parts of the dispersion-As added per 100 parts of copolymer (dryweight). This causes the latex to gel within 5 minutes. The foam isplaced in a mold such as a closed aluminum mold for a mattress or thelike, is allowed to gel, and is then cured for one hour at 100 C.Examination of the cured mold will show no shrinkage.

to 5 per cent of any of the amines mentioned may be employed. The tablegives additional information which serves as a guide in employing thedescribed procedure with the amines mentioned.

Shrinkage data Amine Percent Shrinkage mum aturlng Gelling Time AgentName cent External Internal (Days) none 0 27 0 4 or more 29 c y c l o he x y l amine l. 0 0 2 i3 Do- 2.25 0 0 0 45 D0. 3 0 0 0-1 53 Do. 4. t 1some 0 47 Do- 6 6 some 0 50 benzylamine 3 0 0 0-4 55 n-grop lamine. 1.8l 0 2 60 nmy mine... 2 0 0 l-Q 54 n-amylamine. 2. 6 0 0 4 51 In theabove table the amount of amine is expressed in grams per 100 gramscopolymer (dry weight). The maturing time is measured in days. As shownby the above table it is not neces sary to mature batches which containeither cyclohexylamine or benzylamine, The gelling agent used issodiumsilicofluoride, and the figures given are the milligramequivalents which testshave shown to be required for gelling 100 grams(dry weight) of copolymer latex in 5 minutes.

At times it has been found desirable to use natural latex withthe'copolymer latex. When over fifty per cent of natural latex is usedthere is no substantial gel shrinkage. Using less than fifty per centnatural latex, such shrinkage is prevented as above described.

The example is illustrative, and may be made therein without departingfrom the I invention which is defined in the appended claims.

What we claim is: v

1. The process of producing sponge from latex of rubber-like copolymerof a conjugated diene from the class consisting of butadiene,piperylene, cyclopentadiene, dimethylbutadiene, isoprene,Z-cyanobutadiene and 2-methyl-l,3-pentadiene, and a'vinyl aromaticmonomer, which comprises producing a foam which includes, in addition tothe copoiymer, vulcanizing ingredients, gelling agent and about 1 to 5per cent. based on the 00-.

polymer, of a gel-shrinkage-reducing agent from the class consisting ofcyclohexyl, benzyl, n-

prop'yl, n-butyl, and n-amyl amines, casting'the foam, gelling, andthencuring it.

2. The process of producing sponge from foamed latex of rubber likecopolymer of a conjugated diene from the class consisting of butadiene,piperylene, cyclopentadiene, dimethylbutadiene, isoprene, 2-cyanobutadiene and 2- methyl-l,3- pentadiene, and a vinyl aromaticmonomer, which comprises producing a foam which includes, in addition tothe copolymer, vulcanizing ingredients, gelling. agent and about 1 to 5per cent, based on the copolymer, of a gelshrinkage-reducing agent whichis a soap of an amine of the class consisting of cyclohexyl, benzyl,n-propyl, n-butyl, and n-amyl amines, casting the foam, gelling, andthen curing it.

3. The process of producing sponge of foamed latex which comprisesfoaming a mixture of latices'consisting mostly of rubber-like copolymerof a conjugated diene from the class consisting of butadiene,piperylene, cyclopentadiene, dimethylbutadiene, isoprene,Z-cyanobutadiene and 2- methyl-1,3-pentadiene, and a vinyl aromaticmonomer and containing latex of natural rubmodifications.

ber and in addition, containing vulcanizing ingredients, gelling agentand about 1 to '5 per cent, based on the copolymer, of agel-shrinkagereducing agent from the class consisting of cyclohexyl,benzyl, n-propyl, n-butyl, and n-amyl amines, casting the foam, gelling,and then curing.

4. The process of producing sponge from latex which comprises roaming alatex composed essentially of rubber-like copolymer of butadieneandflstyrene which contains .vulcanizing ingredients, gelling agent andabout 1 to 5 per cent, based on the copolymer, of agel-shrinkage-reducing agent from the class consisting of cyclohexyl,benzyl, n-propyl, n-butyl, and n-amyl amines, casting the foam, gelling,and then curing.

5. The process of producing sponge from latex which comprises foaming amixture of latex composed largely of rubber-like copolymer of butadieneand styrene and containing natural rubber latex, which mixture containsvulcanizing ingredients, gelling agent and about 1 to 5 per cent, basedon the copolymer, of a gel-shrinkagereducing agent from the classconsisting of cyclohexyl, benzyl, n-propyl, n-butyl, and n-amyl amines,casting the foam, gelling, and then curins.

6. The step in the process of producing sponge from latex of rubber-likecoplymer of butadiene and styrene which comprises incorporating in afoam thereof. in addition to suflicient sodium silicofiuoride to eii'ectgelling, about 1 to 5 per centof cyclohexylamine.

7. The process of producing a sponge from latex which contains no rubberother than natural rubber and rubber-like copolymer of ,butadiene andstyrene, and the rubber content of which is at least fifty per centrubber-like copolymer of butadiene and styrene, which process comprisesproducing a foam which in addition to the latex includes vulcanizingingredients, 9. gelling agent, and one to five per cent (based on thecopolymer) of a gel-shrinkage-reducing agent from the class consistingof cyclohexyl, benzyl, n-propyl, n-butyl, and n-amylamines, casting thefoam, gelling, and then curing it.

8. The process of producing a sponge which comprises making a firstdispersion of three parts by weight of cyclohexyl amine and two parts byweight of potassium castor oil soap, making a second dispersion of twoparts by weight of sulparts by weight of sodium silicofiuoride as adispersion to the foam, transferring the foam to a mold and allowing itto gel, and then curing it for one hour at C.

9. The process of producing sponge from late: 0) rubber-like copolymerof a conjugated diene from the class consisting of butadiene,piperulene, cyclopentadiene, dimethyllmtadiene, isoprene,z-cyanobutadiene and 2-meth1ll-1,3-pentadiene, and a vinyl aromaticmonomer, which comprises producing a foam which. includes, in additionto the copolymer, a ael-shrinkage-re- I ducing agent from the classconsistin of cyclohexyl, benzyl, n-propyl, n-butyl, and n-amyl amines ina small amount not greater than about 5 per cent (based on thecopolymer) vulcanizing ingredients and gelling agent, casting the foam,gelling, and then curing it.

10. The process of producing sponge from foamed latex which comprisesfoaming a mixture of latices consisting mostly of rubber-like c'opolgmerof a coniiugated'diene from the class consisting of butadiene,piperylene, cyclopentadiene, dimethylbutadiene, isoprene, 2cyanobutadiene and 2-methyl-L3-pentadiene and a vinyl aromatic monomerand containing latex of natural rubber and in addition, containing agel-shrinloage-reducing agent from the class consisting of cycloheccyl,benzyl, n-propyl, n-butyl and n-amyl amines in a small amount notgreater than about 5 per cent (based on the copolymer), vulcanizingingredients and gelling agent, casting the foam, gelling, and thencuring.

' 11. The process of producing sponge from latex which comprises foaminga latex composed essentially of rubber-like copolymer of butadiene andstyrene which contains a get-shrinkage-reducing agent from the classconsisting of cyclohexyl, benzyl, n-propyl, n-butyl, and n-amyl aminesin a small amount not'greater than about 5 per cent (based on the'copolymer), vulcanieing ingredients andgelling agent, casting the foam,gelling, and then curing.

12. The process of producing sponge ol'foamed latex which comprisesfoaming a mixture of latices consisting mostl of rubber-like copolymerof butadiene and styrene and containing latex of natural rubber and inaddition, containing a gelshrinkage-reducing agent from the classconsist ing of cyclohexyl, benzyl, n-propyl, n-butyl, and n-amyl aminesin a small amount not more than about 5 per cent (based on thecopolymer), vulcanizing ingredients and gelling agent, casting the foam,gelling and then curing.

y 13. A process of producing sponge of foamed later: which comprisesfoaming a mixture of latices consisting mostly of rubber-like copolymerofbutadiene and styrene and containing latest of natural rubber and inaddition, containing cyclohezcylamine in a. small amount not greaterthan about 5 per cent (based on the copolymer) as agel-shrinkage-reclucing agent, vulcanizing ingredients and gellingagent, casting the foam, and then curing.

14. The step in the process of producing sponge from latex ofrubber-like copolymer of butadiene and styrene which comprisesincorporating in a foam thereof, in addition to sujficient sodiumsilicofluoride to efiect gelling, cycloheaylamine in a small amount notgreater than about 5 per cent.

LEONARD A. WOHLE-R. ERNST SCHMIDT.

References Cited in the file 01 this patent UNITED STATES PATENTS NumberName Date 1,852,447 Chapman Apr. 5, 1932 2,234,204 'Starkweather et a1.Nov. 11, 1941 2,290,567 MacKay July 21, 1942 2,360,913 Van ValkenburghOct. 24, 1944 2,444,869 Clayton July 6, 1948 2,537,645 Wohler et a1 Jan.9, 1951 OTHER REFERENCES Bachle Kautschuk," October 1937, Jahrg. 13, pp.174 to 176.

